ALERT OPERATORS TRANSMISSION - ALERT OPERATORS TRANSMISSION

AIRBUS CUSTOMER SERVICES

SUBJECT: ATA 25-11-00 SOGERMA PILOT SEAT PN 2510112/2510113-SERIES - UNCOMMANDED HORIZONTAL MOVEMENT
      
OUR REF.:  A25W001-12 dated 06-June-2012.


1. AIRCRAFT AFFECTED

All A300-600 / A300-600ST / A310-200 / A310-300 equipped with SOGERMA Powered Captain and First Officer Seat PN 2510112/2510113-Series.


2. REFERENCED DOCUMENTATION

2.1 Appendix
Appendix 1 - Flow chart and exploded view.

2.2 References

REF. 1 IPC 25-11-01
REF. 2 AMM 25-11-11 (CAPTAIN SEAT)
REF. 3 AMM 25-11-12 (FIRST OFFICER SEAT)
REF. 4 SOGERMA CMM 25-11-19, Rev 10 dated 15-Mar-2010
REF. 5 SOGERMA CMM 25-11-22, Rev 09 dated 15-Mar-2010
REF. 6 ARTUS CMM 25-13-02 dated Jan-2008 
REF. 7 SOGERMA VSB 2510112-25-898 dated 24-Apr-2012
REF. 8 SOGERMA VSB 2510112-25-813 Rev. 03 dated 14-Jan-2010
REF. 9 AIRBUS SB A300-25-6217 dated 31-Aug-2009 for A300-600
REF. 10 AIRBUS SB A300-25-9011 dated 31-Aug-2009 for A300-600ST 
REF. 11 AIRBUS SB A310-25-2205 revision 01 dated 19-Nov-2010 for A310 
REF. 12 AOT A300-25A6215 Rev. 02 dated 02 MAR 2009
REF. 13 AOT A300-25A9010 Rev. 02 dated 02 MAR 2009
REF. 14 AOT A310-25A2203 Rev. 02 dated 02 MAR 2009
REF. 15 EASA Airworthiness Directive (AD) 2010-0070
REF. 16 FAA Airworthiness Directive (AD) 2011-06-09


3. REASON

3.1 FACTS

An Operator recently reported that, during climb phase of an A310 aircraft, the First Officer Seat PN 2510113-55-11 slid back step by step to the end stop position.
Command was transferred to the captain and flight continued uneventful.
After removal of the First Officer seat PN 2510113-55-11, vendor SOGERMA(SOG), it has been identified that the reduction gear of the horizontal actuator PN RT19H4FX (vendor ARTUS) was damaged.

3.2 BACKGROUND

In 2008, AOTs A300-25A6215 / A300-25A9010 / A310-25A2203 were issued to inform A300-600 / A300-600ST / A310 operators of a similar event which occurred on board an A300-600 aircraft and resulted in SOGERMA First Officer seat PN 2510113-05-14 sliding back by itself to the end stop position. 

Investigations on the removed reduction gear of the horizontal actuators PN RT19H4FX showed that the disc key inside the clutch (reflected in ARTUS CMM 25-13-02 Page 1016 Figure 2 Item 100 refer to appendix 1) was broken, thus unlocking the seat horizontal movement.
Detailed operational check of the seat itself revealed that the actuator operation could not be properly stopped by the aft horizontal end stop switch (reflected in SOGERMA CMM 25-11-19 or CMM 25-11-22 Page 1010-0 Figure 10 Item 480 refer to appendix 1).

At that time, SOGERMA provided VSB 2510112-25-813, covered by Airbus Service Bulletins SB A300-25-6217, SB A300-25-9011, SB A310-25-2205 to ensure correct operation of the end stop switch avoiding any further damage to the disc key. 
This final fix has been rendered mandatory by through EASA AD REF 15 and FAA AD REF 16.

3.3 INVESTIGATION:

Regarding the last event, the investigation on the reduction gear of the horizontal actuator PN RT19H4FX removed from First Officer seat PN 2510113-55-11 showed that the disc key inside the clutch (reflected in ARTUS CMM 25-13-02 Page 1016 Figure 2 Item 100 refer to appendix 1) was also broken, thus unlocking the seat horizontal movement.

VSB 2510112-25-813 was previously applied on this removed First Officer Seat.

Detailed operational check of the seat itself revealed that the reduction gear actuator operation could not be properly stopped due to following scenario:
- The disc key was broken inside of the clutch, before the VSB 2510112-25-813 embodiment addressing the end stop switch issue.
- Further to the disc key breaking-off, a jamming occurred between the gear and the shaft of the clutch (reflected in ARTUS CMM 25-13-02 Page 1016 Figure 2 Item 170/60 refer to appendix 1), allowing sufficient torque transmission between the gear and the shaft for normal pilot seat operation.
- During climb, with the high aircraft incidence generating high longitudinal loads on the pilot seat, the jamming between the gear and the shaft was not sufficient to keep the First Officer Seat in locked position, leading to a step by step backward movement.

3.4 CONSEQUENCES

The horizontal locking of the Captain/First Officer Seat is no more ensured if jamming condition between the gear and the shaft of the actuators PN RT19H4FX
clutch is not sufficient, while high longitudinal loads are applied on the seat.

3.5 AIM

The purpose of this AOT is to request A300-600 / A300-600ST / A310 operators to check the horizontal locking function on the Captain and First Officer seats PN 2510112/2510113-Series, by testing the disc key condition in accordance with the instructions of the SOGERMA VSB 2510112-25-898 thus preventing any potential seat movement due to a damaged disc key inside of the reduction gear actuator PN 
RT19H4FX.

4. SHORT TERM ACTION

4.1 PLANNING AND MANPOWER

4.1.1 ACCOMPLISHMENT TIMESCALE

Accomplishment of SOGERMA VSB 2510112-25-898 has to be performed within the next 6 months after the dispatch date of this AOT.

4.1.2 MANPOWER

The estimated time to perform SOGERMA VSB 2510112-25-898 is 0.3 MH per seat.

4.2 DESCRIPTION

4.2.1 ACCESS

N/A

4.2.2 INSPECTION REQUIREMENTS

Inspection of Captain and First Officer Seat PN 2510112/2510113-Series has to be performed as per SOGERMA VSB 2510112-25-898 instructions (please refer to Appendix 1. Exploded view).

4.2.3 FINDINGS

VSB 2510112-25-898 describes a simple procedure to test the disc key condition, by means of a calibrated tensile test sample PN 2510112299-20(Vendor SOGERMA).
The calibrated tensile test sample is screwed between the actuator and the pilot seat base that moves horizontally during normal operating conditions.

If the tensile test sample breaks-off, while activating the electrical horizontal control switch, the actuator is serviceable.

If the tensile test sample does not break-off, it means that the seat locking function is not ensured and it is required, before next flight, to either:
 - replace the pilot seat with a serviceable one as per REF 2 and/or REF 3.
 - or remove the seat, for replacement of the actuator PN RT19H4FX as per REF 4 and/or REF 5.

Note: A sampling has been performed on a representative number of aircraft showing that none of the inspected seats required pilot seat or actuator replacement.

4.3 SPARES AND TOOLING

Dedicated information letter will be provided by SOGERMA to support operators in case of findings (i.e. tensile test sample does not break-off)
Standard tooling and test kit PN: 25-898-9000 are needed for accomplishment of VSB 2510112-25-898.

5. FURTHER INFORMATION

5.1 FOLLOW-UP PLAN

An Airworthiness Directive is expected to be issued by EASA, to render mandatory this AOT.
No specific follow-up is foreseen for this AOT, as SOGERMA VSB 2510112-25-898 is a one-shot inspection.

5.2 IMPACTED DOCUMENTATION

N/A

6. AOT APPROVAL

The technical content of this document is approved under the authority of DOA nr. EASA.21J.031.

7. REPORTING

Operators are requested to acknowledge receipt of this AOT within 48 hours after receipt to:
Mrs. V. HOLDEN, SEEC
E-mail: valerie.holden@airbus.com
Fax number +33 (0)5 61 93 44 25

Questions about this AOT and inspection results with or without findings are to be sent to Airbus Customer Services engineering as soon as possible, after the AOT application, to the attention of:

Thierry BEUCHARD
Cabin Interior Engineer
Customer Services Engineering - SEEC3
AIRBUS
Phone: +33 (0)5 61 93 86 86
Fax number +33 (0)5 61 93 44 25
E-mail: Thierry.beuchard@airbus.com

Best Regards,

J-L MOUYSSET			G. DESESQUELLES
VICE PRESIDENT ENGINEERING SUPPORT	HEAD OF A300/A310 FAMILY PROGRAMME SUPPORT
CUSTOMER SERVICES			CUSTOMER SERVICES